Measuring Apparatus For Monitoring Residual Oxygen In An Exhaust Gas
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Abstract
A lambda probe (1) is used with the measuring apparatus for monitoring residual oxygen in an exhaust gas, in which a measuring point for oxygen in a sensor (2) is connected via a diffusion gap (22) with a reaction chamber (24). During operation of the probe the reaction chamber drives a stream of oxygen IO2 along the diffusion gap by means of a controllably adjustable oxygen partial pressure pi. By means of an electro-chemical, oxygen ion pump driven by an electrical pump current Ip, an oxygen partial pressure pi predetermined as a desired value is set in the reaction chamber. In this arrangement the pump current, the strength of which is proportional to the strength of the stream of oxygen driven along the diffusion gap, can be used as a measurement parameter for the partial pressure pm of the residual oxygen in the exhaust gas or its concentration. The residual oxygen can be monitored during a normal operating phase, the phase N. The lambda probe can be operated for test purposes, at times, particularly intermittently in a phase H or a phase L. In these operating phases H and L the oxygen partial pressure pi in the reaction chamber (24) adopts a largely minimum value or a largely maximum value. By means of changing between the named operating phases, by registering the pump current Ip and by comparing the registered pump currents Ip with empirical values, conclusions with regard to the ability of the probe to function (1) can be derived, so that if necessary, in the case of a lacking or faulty ability to function, measures can be introduced to remedy the deficiencies or to exchange the sensor (2).
12 Citations
16 Claims
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1-8. -8. (canceled)
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9. A method for monitoring residual oxygen in an exhaust gas using a lambda probe (1) in which a measuring point for oxygen at a sensor (2) is connected with a reaction chamber (25) via a diffusion gap (22), which during operation of the probe drives a stream of oxygen IO2 along the diffusion gap by means of a controllably adjustable oxygen partial pressure pi, wherein by means of an electrochemical oxygen ion pump driven by an electrical pump current Ip a predetermined oxygen partial pressure pi is set in the reaction chamber as a desired value and thus the pump current, the strength of which is proportional to the strength of the oxygen stream driven along the diffusion gap, can be used as a measurement parameter for the partial pressure pm of the residual oxygen in the exhaust gas,
wherein the residual oxygen is monitored during a normal operating phase (N), wherein the lambda probe is operated intermittently for test purposes in two phases (H, L) in which operating phases the oxygen partial pressure pi in the reaction chamber (25) adopts a minimum value and a maximum value respectively, and wherein by means of changing between the named operating phases, by registering the pump current Ip and by comparing the pump currents Ip with empirical values, conclusions with regard to the ability of the probe (1) to function are derived so that in the case of a lacking or faulty ability to function, measures can be introduced to remedy the deficiencies or to exchange the sensor (2).
Specification